The invention relates to a residual recording material amount detector suitable for use in a page printer that prints patterns on a recording sheet by forming a latent electrostatic image on a photoreceptor drum using a light beam modulated by print data and causing toner, which is the recording material, to electrostatically adhere to the latent electrostatic image.
With an apparatus for forming patterns on a recording sheet by causing toner to adhere to a latent electrostatic image formed on a photoreceptor drum, a tank containing the toner is accommodated inside a frame, and therefore the amount of residual toner cannot be visibly checked from the outside. To overcome this problem, a built-in sensor serving as a toner detecting device is usually arranged in the toner tank. In such a residual toner amount detecting system, uniform distribution of the toner inside the tank is often disturbed, which imposes the problem that the toner cannot be replaced in the manner of a cartridge, in addition to the problem that the detection accuracy is low.
To overcome this problem, residual recording material amount detectors for a page printer are proposed in Unexamined Japanese Patent Publications Nos. 224363/1983 and 208777/1985. These detectors are characterized as counting individual dot-forming image signals and multiplying such signals by a predetermined value. According to these detectors, since the total number of recorded dots is counted, the detection accuracy is successfully improved and the toner related members can be provided with a cartridge.
However, according to these detectors, the fact that the toner consumption per dot is calculated in advance, and that the toner consumption is multiplied by an integrated number of printed dots leads to the problem that the amount of the residual toner is detected in error depending on the kind of data to be printed.